Process for classifying finely-divided material



w. A. SCHMIDT.. PROCESS FOR CLASSIFYING FINELY D`|VIDED MATERIAL.

APPLICATION FILED AUG-28| 1916.

Patented Apr. 6,1920.

III 1| :mmm

UNITED sTATEs PATENT WALTER A. SCHMIDT, OF LOS ANGELES, CALIFORNIA, ASSIGNOR TO INTERNATIONAL PRECIPITATION COMPANY, F LOS ANGELES, CALIFORNIA, A CORPORATION OF CALI- FORNIA.

rnocnss Eon, cLAssIrYnvG Franny-DIVIDED MATERIAL.

Original application led February 18, 1915, Serial No. 9,066. Divided and this application 1916. Serial No. 117,183.

erty, and particularly to the separation into different parts of suspended material car- Iried by lue or furnace gases or otherwise occurring in the arts.

The main object of the invention is to provide for separation or classification of the material in such manner as to reduce to a minimum the expense of installing and operating the`apparatus for carrying out such operation. A further object of the invention is to provide for carrying out such separation in thev case of .particles too line to be successfully separated or collected by the ordinary processes depending on gravitative settling, centrifugal action or the like.

This application is a division of my, application, Ser. No. 9066, filed February 18, 1915, now Patent No. 1,200,887, granted Oct. 10, 1916, for process of obtaining alkali metal compound.

The accompanying drawings illustrate an apparatus suitable for carrying 'out my invention, and referring thereto.:

Figure 1 is a vertical section of the apparatus Fig. 2 is a horizontal section on line 2-2 in Fig. 1.

In the drawings, 4 designates a flue, stack or other means for conducting a stream or current of gas, containing suspended material of different degrees of ineness. Said stack may, for example, as speciied in my said application, be the stack of a cement burning ln'ln. It may, however, be the outlet flue of anyrfurnace or other apparatus in which fumes or dust are produced, provided such fumes or dust contain particles ofji'erent size so as to be susceptible t0 the operation ifv` this process.

VThis flue is connected to the inlet opening 2 of av casing or chamber 5, said chamber being preferably of considerable length, and

Specification of Letters Patent.

Patented Apr. 6, 1920.

iiled August 28,

having the inlet opening v2 at one end and'V an outlet opening 3, at its other end, communicating with a stack or outlet flue l0. Dampers 2 and 3 are preferably provided at the respective openings 2 and 3, to control the rate of flow through the chamber 5, said dampers being operated by any suitable means, not shown.

Suspended in the'chamber 5 are a series of rows of 'vertical plates l8 constituting collecting electrodes, and a series 4of rows of discharge electrodes 7, formed, for example, as wires hung between the` plates of each row. The collecting electrodes 8 may be hung from a top frame 9, which is grounded as indicated at 16. vThe discharge electrodes are hung from an insulated frame 18 which may be connected by wire-1410 suitable means for supplying high tension current, preferably unidirectional. For this purpose, wire 14 may be connected to a rectiier 13 `of any suitable type which is connected to the secondary winding of a stepup transformer, the primary winding thereof being connected to an alternating current supply circuit 20-21. Rectifier 13 is pro-l' vided with ground connection 22, for completing circuit to the grounded parts 8 of the precipitating apparatus. Discharge electrodes 7 may be held in position by weightsA 7 or otherwise.

Each row of plates 8, with the intervening discharge electrodes 7, constitutes a pre-v cipitating element or portion arranged `transversely of the current lof gas passing through chamber' 5 and adapted to subject such gas to electrical action, so that the gas in' passing successively through the successive elements will be subjected to a succes- `sion of precipitating actions. Collecting or as follows,

- from time to time, if necessary, by any suitable means to cause them to drop into said bins. I have found that in this operation, the larger particles are most readily and quickly precipitated so that thel deposit in the first bins is mostly or 'largely of comparatively large particles, and that the finer particles are more slowl precipitated, so that the material accumu ated in successive bins in the series is progressively lfiner o1: consistsof particles smaller'in size. In eX- planation of this selective action, it may be stated that the larger particles can be more readily charged to the degree necessary for effective 'action of the electrostatic field, while at the same time, the smaller particles offer relatively a greaterresistanceto translation through the gaseous medium, due to the higher relative buoyancy.

rlhe above described process, therefore, provides for selective separation of the particles suspended in thegas, with respect to Q size, and by properly constructing the apparatus as to length' and cross-sectional area of l. i the chamber 5, the number of precipitating elements and receiving bins so as to properly proportion the rate of travel to the rapidity of precipitation of the particles by the elec-- trical action, any desired separation or classication of such material as to size may be provided for.

The cross-sectional area of the chamber 5 is substantially 'the same throughout its length so that the rate of flow or velocity of the gas is substantially uniform throughout the travel thereof in said chamber and the gas passes with such rapidity through the series of field portions or sections that substantially the same conditions as to temperature exist throughout the body ofvgas, the difference in precipitating action as to successive lselective precipitation of progres- Sively finer particles resulting from the time of exposure to electro-precipitating action rather than to difference of temperature. My process is also distinguished from processes involving the use of a precipitating chamber of progressively increasing crosssectional areaso as to produce progressive retardation of the gas with resultant selective precipitation of the 'progressively finer mastantially uniform, as above stated, so that the selective precipitation is due to the time element, as above explained.'

The process described is applicable also for separation of ore constituents passin off as dust and fume from smelters, or the l(like, and in such cases, as well as in the case of cement dust, the selective separation as to size may result also in selective separation as to chemical constitution of the particles.

While my invention is'particularly intended for selective precipitation of suspended material present in the eiiiuent gases of furnaces or kilns, it is capable of other applications, for example-the material to be classified may be taken from a body ofv such material, such as a pile or body of finely divided silica, ore or other rock, and distributed into a stream of air or other gas, by blowing or injecting it into such gas, and the gas containing the suspended particles of different degrees of fineness may then be passed through the series of' precipitating is required -for precipitation of the finerv particles. It will be understood that the selection or separation by this process is not necessarily sharp, as more or less of the ner material may be precipitated along with the coarser material. Thus, in applying the invention in connection with cement dust, as described in my application aforesaid, more or less fine particles, consisting largely of potassium compounds, may be precipitated preclpitating elements of the series; but the separation so effected is sufficient for many purposes, and in any case wherein it is not sufficient, a closer separation may be effected by passing the precipitated material from any one or more of the bins 11, back to the supply fiue 4, and acting on it a second time in the same apparatus, or in another apparatus.

As described in my prior application-I aforesaid, my process may be advantageously employed in selectively separating potasslum compound to a greater or less degree, from the other materials present in the dust passing from cement kilns. The present invention, when so applied, constituting a step in the complete process'of volatilizaalong withthe coarser. particles in the first l terials, the velocity of gas How being subtion, condensation and selective precipitation disclosed and claimed in said applicadescribed, or by mechanical action, as by blowing or injecting the finely divided material into the gas precedent to the precipitation action.

What I' claim is:

1. The process of selectively separating particles of different size suspended in a gas, which consists in passing the gas successively, at substantially uniform velocity through a series of velectric fields of substani F" tially similar intensity and substantially uniform cross-sectional area to produce a succession of electrical actions on the gas in su'ch manner as to precipitate successlvely particles of progresslvely smaller size and collecting separately the different sizes of precipitated particles..

2. The process of selectively separating,

as to size, particles suspended in a gas,v

which consists in passing the gas in a stream of substantially uniform cross-sectional area and substantially uniform velocity through a series of electrical fields, all presenting tions, in such manner as to cause recipi-4 tation of `partlcles of dlflerent neness mainly in different eld portions and collecting separately the different sizes of precipitated particles.

,- 3. The process of selectively separating as to4 size particles suspended in a gas, which consists inpassing the gas between successive electric-eld portions of y'substantially uniform cross-sectional area presenting suffi'ciently high potential difference to cause ,precipitation ofthe particles from the gas,

the travel of theV particles between theelectrodes during the time of vprecipitation being suflicient to cause the smaller' particles to be precipitated separately from" and subl sequent to the larger particles and collecting separately the different sizes of precipitated particles. A

4. The process of selectively separating particles of different size suspended in a gas, which consists in successively passing the gas between successive electricalv field portions, the rate ofl iiow of the 'gas being substantially uniform throughout the operation and being so proportionate relative tothe rapidity ofI electrical precipitation by the successive field portions, that the iner and more d'iflicultly precipitable particles are carried beyond the place of precipitation of the coars'er particles andl are precipitated separatelyl therefrom and collecting separately the diHerent sizes of precipitated particles.

In testimony whereof I have hereunto set my hand, at Los Angeles, California, this A18th day of August, 1916. substantially the same electrostatic` condip. v

n WALTER A. SCHMIDT. 

